Explicit data type conversion for numeric field

When i try to generate a excel chart from vb, in my system it works fine. whatever the value i assign to that excel sheet it accepts. But when i try to run the project in my friends system, it request the explicit data type conversion for numeric field. i m not able to assign the number field after assigning the string field. Why its happening? Kindly give solution.

that might be because of some system settings or some required system files are missing.